1. Field of the Invention
This invention relates generally to the design of a bipolar electrosurgical scissors, and more particularly to a surgical scissors incorporating bipolar electrodes on its blade elements, such that mechanical cutting with subsequent electrocoagulation can be achieved without requiring an instrument exchange.
2. Discussion of the Prior Art
Electrosurgical devices are well-known surgical instruments used in coagulating and cutting procedures. Electrocoagulating instruments include at least one conductive electrode. Radio frequency energy is conducted through this electrode to either a remote conductive body-plate (monopolar) or to a second, closely-spaced conductive electrode (bipolar). Current passing through the gap between the two electrodes will coagulate blood and other body fluids placed between the two electrodes.
Monopolar electrocautery instruments suffer from the fact that the return path between the active electrode and the large area body-plate can be unpredictable as the electrical current seeks the return electrode through the path of least resistance. With bipolar electrosurgical instruments, however, because the two electrodes are closely spaced to one another, usually at the distal end of an instrument handle, the return path is very short and involves the tissue and fluids in the short path between the electrodes. Although there is available in the prior art monopolar scissors where both of the scissors blades form one conductive pole and with a remote body plate being the second pole, such a scissors still has the drawbacks of being a monopolar device.
The prior art also contains a scissors-type instrument for mechanically snipping tissue during the course of an endoscopic procedure. Such a scissors comprises a pair of blades fabricated from metal and disposed at the distal end of an elongated tubular member whose outside diameter is sufficiently small to allow it to be passed through the working lumen of an endoscope, a laparoscope or other similar devices known in the art. Disposed at the proximal end of the rigid tube is a scissors-type handle having a pair of members pivotally coupled to one another, each with a finger-receiving loop. An appropriate mechanical coupling is made between the handle members and the blades so that manipulation of the handle members will result in an opening and closing of the blades relative to one another. When using a mechanical cutting scissors of this type to excise tissue, bleeding results when a blood vessel is cut. At that point, it is generally necessary for the surgeon to remove the scissors instrument from the working lumen of the endoscope and then insert an electrocoagulator down the endoscope to the site of the bleeder. This instrument exchange is time-consuming and in a surgical procedure where moments count, it would be desirable to have a scissors-type instrument for cutting but which also incorporates the ability to coagulate blood and other body tissues using RF energy.
With metal-to-metal contact along the sharpened edges of the two blades, an electrical short results if the two blades act as separate electrodes of a bipolar pair. Furthermore, the attempt to use a metal rivet or screw as the pivot point for the blades is another area where short-circuiting is likely to occur. When such a short exists, the electrical current does not flow through the blood or body tissue to effect coagulation, but instead, follows the short-circuit path from one electrode to the other. This has been addressed in the prior art by a scissors with conductive metal blade supports to which sharpened metal cutting blades are affixed using a nonconductive epoxy bonding and spacing layer. In this regard, reference is made to the Rydell U.S. Pat. No. 5,352,222 assigned to the assignee of the present invention. The manufacture of such a scissors involves the somewhat time consuming process of bonding the cutting blades to the metal blade supports.
Another prior art scissors, disclosed in the Rydell U.S. Pat. No. 5,356,408, assigned to the assignee of the present invention, incorporates honed ceramic cutting and shearing surfaces on the opposed interior surfaces of metal blade support members. The blade support members are wired to act as electrodes. However, ceramic is a fragile, brittle material and the grinding operations for ceramic can be expensive. Furthermore, the ceramic surfaces must be affixed to the metal blade members in a way that prevents delamination during use.
To date, however, there is not available in the marketplace a bipolar electrosurgical scissors having two metal blades pivotally joined to one another with an insulating layer applied to the non-shearing surfaces of the blades and with electrodes located on the insulating layer of the blades and which are, thus, electrically isolated from the metal cutting edges and shearing surfaces of the blades. A need therefore exists for a bipolar electrosurgical scissors for use in both open and endoscopic surgical procedures where the shearing surfaces may be surgical steel, but where the exterior surface portions of the metal blades can be coated or otherwise provided with an insulating layer on which conductive metal electrodes are disposed, allowing the scissors to be used in performing bipolar electrocoagulation as the cutting progresses.